Variable pitch propeller



Dec. 25, 1945. M. GREGOR VARIABLE FITCH PROPELLER Filed Oct. 22, 1943 2 Sheets-Sheet l 0m. @n EN INVENTOR Mzjchae Gregor BY ATTORN EY Dec. 25, E945. M. GRI-:Goa

VARIABLE FITCH PROPELLER 2 Sheets-Sheet 2 Filed 001;. 22, 1945 INVENTOR Mic/wl @regar ATTORNEY Patented Dec. 2S, l1945 I UNITED STATES PATENT OFFICE j VARIABLE vPrrcn PROPELLER v Michael Gregor, New Yoran. Y. Application October 22, 1943, Serial No. 507,244

comms. (ci. 17o-162) This invention relates to propellers for aeroplanes and .other vehicles which derive traction through propeller-driven media; more particularly my invention relates to propeller constructions whereby the pitch of the propeller is automatically adjusted to meet various requirements in use.

Known to me is the provision of propellers for flying machines and the desirability of altering the pitch of the propeller to meet conditions in use, such as take-off, climbing high speed" and cruising speeds. These devices largely include manual operation under the control of the pilot, leaving it to his judgment what setting of the pitch of the propeller is to be employed to meet the conditions confronting him, such as take-off, climbing orcruising speeds.

The design for the best aero-dynamic efficiency of the propeller dictates a predetermined rotational speed which, for securing the primary eiciency of design, should eliminate the human'element of adjustment.

The primary purpose of my invention is to provide a variable adjustment of the propeller whereby, automatically and without manual control, the pitch of the propeller is maintained to secure a high operating efficiency during all service conditions such as take-off, climbing and cruising" and high speeds; and vice versa, in descent and in landing; while at the same time leaving the pilot in full control of the full power of the engine as may require over speed to meet the exigencies of landing operations which may confront him. l

My invention is predicated upon and has as its object to provide the use of the centrifugal force generated during rotation ofthe propeller to effect an automatic increase in the pitch of the propeller upon encountering a desirable rotational speed of the propeller shaft and to include means progressively to increase the pitch of the propeller during cruising speeds, and to hold the pitch of the propeller at the most efcient pitch irrespective of the centrifugal force which was utilized to convert the pitch of the propeller as a preliminary operation such as in steps of (l) take-off and (2) climbing More specifically, it isan object of my invention to provide an automatic variable pitch propeller characterized by maintenance of alow pitch with the employment of yhigh engine speed for take-olf, and further characterized by achieving medium pitch with high speed for climbing, and still further characterized by construction for achieving high pitch with low'engine speeds for cruisingl after having gone through thecycle of the first two steps noted.

Still further objects of my invention reside in the provision of an automatic pitch propeller characterized by the inclusion of a means whereby predetermined low pitch is maintained with high engine speed for take-off and the inclusion of centrifugally controlled means for increasing the pitch of the propeller for climbing and adjusting the pitch of the propeller to maximum high pitch,- combined with means for holding and maintaining the achieved high pitch position of the propeller within predetermined lower engine speeds for maximum eiciency of cruising Still further objects of my invention reside in the provision of an automatic pitch propeller which includes means to increase the pitch of the propeller by centrifugal force and to maintain a predeterminedly desirable pitch of the propeller irrespective of the engine speed utilized to set the pitch of the propeller, whereby maximum eficiency is secured during cruising thereby making available to inexperienced pilots the adjustment of the pitch ofthe propeller for most economical cruising at the lowest effective revolution of the engine propeller.

Still further objects of my invention reside in the provision of a propeller mounting assembly in which the mostecient pitch position of the blades is maintained, predicated upon the desirable attributes of the propeller, designed to operate approximately at, or precisely at, a constant speed factor, by taking into account that the employment of an -aero-dynamical neutral aerofoil section of the blades of the propeller will improve the functioning of the variable pitch control device.

Still further objects of my invention reside in the provision of a variable pitch propeller which is simple in operation and inexpensive in cost.

For the attainment of the foregoing objects and such further objects asmay appear herein or be hereinafter pointed out, I make reference to the accompanying drawings forming a part hereof, in which:

Figure 1 is a longitudinally fragmentary sectional view of the hub portion of my device taken on the line I-I of Figure 3;

Figure 2 is a section taken on the line 2-2 of Figure 1:

Figure 3 is a section taken on the line 3-3 of Figure 1;

Figure 4 is a. fragmentary sectional view taken on. th line 4--l of Figure 1;

Figure 5 is an enlarged detail taken on line -5 of Figure 3;

Figure 6 is a perspective View of the centrlfugal- 7 eiected weight balance;

Figure 7 is a fragmentary sectional view with he weight in the neutral position.

Making reference to the drawings, I have shown hub housing I arranged to be mounted upon he engine shaft by the boring I I formed therein. The hub housing I0 has its ends I2 formed to re- :eive the propeller blades I3. The axial ends of he blades being .fitted by shrinking or casting vlthin a sleeve I4. This sleeve, in turn, is .hreaded at I to engage the ange I6, cooperatng with the seat I1 to hold there-between the hrust bearing I8, constituting the ball races I9 md ball bearings 20. The forward end of the rousing adjacent the opening I2 is provided with :paced flanges 2l-2I in the annulus between which there is positioned a second ball race 22. A collar 23 engages a threaded portion 24 on the sleeve I4 to hold the inner end of the blade in rotational position in the bearings I8 and 22 just :Iescribed.

The ilange I6 is provided with an axial boring Il which is provided withan internal helcallylplined portion 25. Within the helical portion there is fitted, diametrical to each other, centrifugally actuated weights 21 shown in Figure 6, comprising an external helically-splined stud 28 rigidly aiiixed to the weight 21 `just described. It will be understood that axial slidable movement oi' the weight member 21 with the splined portions 26 and 28 in engagement with each other willV serve to rotationally move the propeller blades I3-I3 within the housing I0 in the bearings I8 and 22 previously described. Ihe weight 21 is formed with ears 29-29 to which is connected toggles 30 comprising legs 3| which fit between the ears and are held in this position by the cross-pin 32. The upper end of the toggle 30 is formed with spaced knuckles 33 embracing the link 34 and'being held in this position by the pin 35 passing through the knuckles 33 and a bearing orifice formedin one end of the link 34. The opposite end of the link 34 is pivoted between the ears 36 formed and projecting from theinner side of the housing I Il.

gles to the axial line of the boring I I of the webbing 50 there is aflixed radially directed legs 5I-5I, as will be more clearly apparent from an inspection of Figures l and 2. These legs are carried by the collar 52 and are each provided with radial slots 53. Between these legs there are4 positioned arcuately-shaped links 54 whose It will thus be observed that radial movement I o! the weight 21 radially perpendicular to the axial line through the boring II may be effected while preventing rotational movement of the spline 28, carried by the weight 21. The toggles 30, heretofore described, eachcarry between their free ends anchor pins 31 upon which are mounted anchoring eyelets 38 and 39 (see Figure 5). The anchoring eyelet 38 is provided with a flange 48 through which headed pins 4I pass. These pins further pass through plate 42 at the opposite end of spring 44, each end of the pins being appropriately headed to prevent removal from the eyelet and plate, respectively. 'I'he plate 42 is formed with a central enlargement 43, axially to position the last convolution of the spring 44. A second plate 45 formed with orifices 46 is mounted for sliding movement upon the pins 4I (four of these being used). formed with a central orice 41 to receive the headed link 48, the free end of which 49 is screwthreaded by or otherwise amxed to the anchoring eyelet 39 previously described. It will thus be seen that separation of the toggles 30 from each other is by a compressive force which is against the expansion force of the spring 44.

Centrally positioned substantially at right an- 'I'his plate 45 is inner ends 55 are guided to move radially by the pin 56 whose ends slide within the slot 53. The opposite outer ends 51 of the links 64 are anchored at the rear face of the weights 21 in slots 58 there provided and by passing the crosspin 59 through orices formed adjacent the ends 51 of the links 54 previously mentioned. It will be observed from the construction just described that by the employment of the links 54 and the slots 53 in the upstanding legs 5 I, that the movement of the weights to and from each other is equalized as the weights and the parts carried thereby move from the position shown in full lines in Figure 1 to the position shown in dotted lines in Figure 1. The movement of the weights 21 can only be eiected against the compressive resistance of the spring 44. Suitable means may be used to minimize the friction in movement of the spring parts, as will be readily understood. This is accomplished when the centrifugal force of rotation moves the weights from the position shown in dotted lines or that shown in Figure 7,

outwardly from the center to the position shown in full lines in Figure 1 and Figure 4. By reason of the splined connection between the stud 28 and the internally splined portion of the iiange 26, the blades are given a rotational eiect, varying the predetermined pitch of the blades I3.

In accordance with my invention to design the propeller blades to maintain best efliciency at approximately or precisely constant speed of the propeller when it has maximum pitch at cruising speeds, I have designed the spring tension of the spring 44 to resist movement by the centrifugal action imparted to the weight 21 until a predetermined engine speed is achieved; say, 5% over normal rating, with the springs drawing the weights toward each other, and with the propeller blades then at low pitch. This is a condition achieved and found desirable in take-off. As momentum of the vehicle is secured to the point where it is desirable to climb, increase in the engines speed beyond the above predetermined rated speed brings into play the centrifugal force which overcomes the spring tension of the spring 44 to move the weights away from each other and thereupon progressively increases the pitch of the propeller. When the predetermined height has'been reached and the pilot levels off, the engine may be accelerated to higher speeds forcing the weights to the maximum position shown in Figures 1 and 4. It now becomes desirable, because of the design of the propeller blades, to maintain a constant speed for cruising to secure maximum eiiiciency, then to lower the engines rotational speed while still holding the maximum pitch of the blades, or to operate at high speeds with the maximum pitch at the rated R. P. M. of the engine. For this purpose I -provide a pitch setting, and within a limited action, a pitch holding member in the form of a pressure detent 60 comprising a sleeve 6I which is conveniently screw threaded at one end 62 into a boring 63 in the wall of the housing I0 previously described, in a-direction generally in parallelism to the boring II arranged to receive the engine drive shaft. The shell 6I is open at its lower end 64 and within this is .lock nut 14 serves shown in Figure "I, which is of the weights contact the abutment moves, gaining mounted the vpin 65 which holding the roller'61 by a cross-pin 68. The upper end ofl the pin 65 proects within the sleeve has spaced legs 66' 64 and is urged outwardly-by the spring 69 actpredetermined pressure, within limits, may be' exerted upon the spring 69 and, in turn, on the roller 61 The roller 61 of the detent normally lies in the path of one edge 15 ofthe weight 21. This is formed. at its outer end with a camming edge 16 anda latching lip 11.

When viewed with the weights in the position the condition of the weights withthe propeller blades and before predetermined centrifugal action displaces the weights outwardly, the roller 61 of the detent lies in the path ofthe edge 15 of the same. As centrifugal forces move the weights from the axial position to the limiting position where the face-18 19 of the flange I6, the limiting angularity of pitch of the propeller blades has been reached. This movement serves, rst, to have the camming surface 16 engage the roller 61 and displace it against the compressionl of the spring 69 and then as the limiting position ofthe weights 21 is reached, the

rider 12 which is urged pitch position.

at the end of the climb and the leveling of! by the P1106.

ished, bythe reduction in engine speed the pitch setting mechanism 6| comes into play to engage the latching lip 11. on the weights, thus automati- ,cally holding the propeller blades in maximum The pilot may then throttle.v

down, within limits, the engine speed for cruising while. the propeller blades are thus held in the high pitch position by the pitch setting member 60, and this position is maintained notwithstanding the insufficiency of hold the Vsplined studs in the extreme position.

the centrifugal force to At landing, the pilot throttles down the engine speed further. 'When the revolutions of the propeller drop out below a predetermined speed, the springs 44 overcome the restraining action of the pitch holding member 60 and the propeller returns Ato low pitch.

If the landing attempt is not successful, the pilot is in full control to'use the full power of the engine with over-speed, as may be necessary to "-pull out again and try another landing, as the blades lie somewhere between low pitch and high pitch and are adjustable automatically to high pitch or intermediate climbing pitch as the pilot may find it necessary to over-speed the engine.

It will be understood that while I have shown a pitch holding member and centrifugally actuat able weights responsive to increase and decrease of engine speeds, -thevmovement of these parts roller 61 falls into latching engagement with the e latching lip 11, restraining inward movement of the weights, notwithstanding any. decrease in rotational speed of the propeller thatis best determined for cruising and the consequent tendency -of `the spring 4 4 to drawv the-weights back towards `the center. .Y -f

In this way,l notwithstanding the diminished rotational speed of the propeller shaft the maximum pitch ofthe propelleris maintainedv by vthe pitch setting member `60.

' It will'be observed from the description thus far 1 made, that by Amy construction the following operation of the mechanism is secured: l.

With'the propeller shaft quiescent, the mechanism takes the"po'sition shown in dotted lines in Figure 1 with thewei'ghts 21 in the position shown in Figure '1. I Rotation of the engine maintains this position with the blades located at the predeterminedly -de'signedminimum pitch.` This is the desirable condition oi! the blades for takeoi. l Asthe engine speed is increased, the spring 44 acting uponthe toggles3ll retains the weights andtherefore the-minimum pitch ofthe propeller may be stabilized to smoothen out a change in Aposition by suitable inertia dampening means known in the art.

By the mechanism that my device takes into account the moment of forces around the longitudinal axis of rotation of the propeller blades. producing such a moment of force:

(l) The aerodynamical moment *produced by the blades having an aerofoil vsection due to movement of the blades in the air. (2) The centrifugal twisting moment by the shape of the blades.

created (3) The moment of force supplied bythe `conl trolllng'device.

e na-rilylrequiredv to be overcome blades I3 as'during take-off. As the plane desirable to over-speed the engine and the -propeller group' and f the springs 44 .are-f *designed accordingly. Gradually the iriecessity of overspeed--i-'is diminishing and the lnormal speed of operation of the engine is' essential. As the resistance of the air density diminishes, as apredetermined factor the engine speed is increased and the weights are moved progressively to an intermediate position graduallyas they overcome momentum or 'initial climb, it is the resistance of the spring` 44 increasing the pitch until the maximum displacement and maximum high pitch position is achieved. This occurs force whereby The design of the propeller blades is made so as to balance the above moments of forces and practically relieve the actuating mechanism from interi'erences and the unnecessary friction ordiin putting the actuating mechanism into play.

Thus, vin accordance with my invention, it will 'be observed that acknowledging the primary efciency is to design the propeller to -secure maximum eiilciency by maintaining an approximate or 'l precisely constant speed, my invention makes possible the adjustment of the pitch and the auto-4 vmatic releasing of the maximum pitch to' give the desirable performance and desirable variation of the pitch of the propeller. r

My invention, it vwill vbe observed, has the advantage vobtained by the use of a restraining force in the linkage system'v actuated by centrifugal deection of the resilient-force can bev reduced and' the desired tension can be obtained at various positions of the masses linked to the resilient force. y

It will be further observed that my invention, by the use of compression' springs, lpermits the retainmentof the necessary ratio lof the resilient force at the rotational speed variation of the pro-v peller. Y

It will be further observed that in view of the The centrifugal. force being thereafter diminprovided, it will be observed There are'three factors settings of the ypitch of the propeller to employ an aero-dynamically neutral section of the blades, there is secured an improved adjustment of the variable pitch control device.

It will be understood that while I have shown and described a splined stud v28 for securing the rotational effect of the propeller, other means willsuggest themselves for securing relative rotation of the propeller blade upon centrifugal displacement of the weights restrained by the springs 44. l

It will further be observed that while my invention secures the most desirable functioning bythe utilization of all of the elements assembled, novelty is attributed to segregated portions thereof, as will be more clearly emphasized in the appended claims and, thereforemy invention is not to be limited to the utilization of the specifically described associated elements.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent, is:

1. A variable pitch propeller comprising, in combination, a hub adapted to be mounted on a propeller shaft, a housing associated with the hub and formed with radially-disposed openings therein, propeller blades journalled within said openings, thrust bearings restraining outward movement of the blades in their journal supports, means for varying the pitch of the blades due to angular velocity of the, propeller, such means comprising va weight associated with each blade positioned within the housing, each of the weights being adapted to move radially outwardly by centrifugal action upon rotation of the propeller, a driving element associated with the weight for increasing the pitch of the blade as such weight moves outwardly, and a driven element associated with the inner end of the blade, one of such elements comprising a helical mem-1 ber, and the other of such elements comprising a member contacting the helical member,means for restraining-outward movement of the weights including compression springs positioned between the weights, rods connecting each end of the springs with the weight positioned adjacent to the opposite end of such springs, whereby outward movement of the weights at opposite ends of the spring will cause compression of such spring, lever means for equalizing outward movement of theopposed weights, and adjustable, spring-pressed detents for retaining the weights in their outermost positions, against the action of the compression springs tending to retract the weights, until the angular velocity of the propeller has decreased to a predetermined maxi mum, l

2. A variable pitch propeller comprising, in combination, a hub adapted to be mounted on a. propeller shaft, a housing associated with the hub and formed with radially-disposed openings therein, propeller blades journalled within said openings, thrust bearings restraining outward movement of the blades in their journal supports, means for varying the pitch of the blades due to a driving element associated with the weight for angular velocity of the propeller, such means vcomprising a weight associated with each blade .straight-line, non-rotational movement thereof radially of the propeller shaft, as a result of centrifugal action due to rotation of the propeller,

increasing the pitch of the blade as such weight moves outwardly, and a driven element associated with the inner end of theblade, one of such elements comprising a helical member, and the other of such elements comprising'a member contacting the helical member, means .for restraining outward movement of the weights including compression springs positioned between the weights, rods connecting each endof the springs with the weight positioned adjacent to the opposite end of such springs, whereby outward movement of the weights at opposite ends of the spring l will cause compression of such spring,V lever means for equalizing outward movement of the opposed weights, and an adjustable, springpressed detent associated with each weight for retaining such weight in its outermost position, against the action of the compression springs tending to retract the weights, until speed of rotation of the propeller has decreased to a predetermined maximum.

3. A variable pitch propeller comprising, in combination, a hub adapted to be received on a propeller shaft, a housing associated with the hub and formed with radially-disposed openings' therein, propeller blades rotatably mounted with- .in said-openings, the inner end of each blade having a longitudinal bore therein, thrust bearings restraining outward movement of the blades in their journal supports, a weight associated with each propeller blade positioned within the housing,each of said weights being adapted to move radially outwardly, due to centrifugal action, upon rotation of the propeller, means for imparting partial rotation to the blade upon such outward movement of the weight, thereby increasing the pitch of said propeller, said means including a stud carriedbby the weight and formed with a helical element on the periphery of'such stud, the bore in the blade being provided with a follower element which is contacted by the helical element, imparting rotation to the blade as the stud moves radially, means for restraining outward movement of the weights including compression springs positioned between the weights, rods connecting each end of the springs with the weight positioned adjacent to the opposite end of such springs, whereby outward movement of the weight will cause compression of the springs, lever means for equalizing outward movement of {the opposed weights, and adjustable, springpressed detents for retaining the weights in their outermost positions, against the action of the compression springs tending to retract the weights.

MICHAEL GREGOR` 

